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Clearing Space Junk

So, I hear on the radio today how they’re planning to adjust the orbit of space junk using lasers. Basically they identify space junk that might collide with a satellite we care about, then they push it with a laser so as to adjust the orbit enough to avoid collision. They’re also talking about launching satellites that can intercept large space junk and de-orbit it.

My thought – why try to de-orbit space junk? We spent a lot of money getting that stuff into space, it’s almost certainly made out of materials we could do something with. People are talking about intercepting asteroids so as to mine them, and build space habitats or other cool stuff. Why can’t we do the same with space junk?

My plan would involve a satellite that basically bounces from item to item of space junk, and pushes each one into a standard orbit – so you end up with a collection of junk all in one place.

My logic is that in order to move around orbits you need two things: energy and a reaction mass. So, you launch a satellite either with a lot of solar panels (energy) or a reactor of some sort (likely to upset lots of people). You give it a small amount of reaction mass – something you can throw away. The idea here is that you can get thrust by either throwing big things away slowly, or small things away really fast. So imagine that we’re throwing away atoms (ions) really fast. In other words an ion drive. We use this drive to synch up our orbit with some junk. We grab the junk. We strip a bit of the mass from the junk to replenish our ion drive. We then “throw” that junk towards an orbit we’d like it to be in, using the junk as reaction mass to push us towards our next piece of space junk.

The hard part here is probably the math. I’m assuming there’s enough space junk up there that we can generally find a trajectory such that we’re throwing our junk towards our junk pile in the sky, and at the same time throw our satellite towards our next junk. But I’m assuming that there are lots of clever people somewhere who can work that out.

We might also want our satellite to be capable of building stuff out of the junk – so maybe it’s capable of attaching a small solar sail to it, along with a control unit so that the junk can now refine it’s orbit sufficiently to join our junk pile properly. And maybe we might need another satellite that’s managing the junk pile – stitching it all together, breaking it down, and making stuff out of it.

Turning space junk from a cost into a profit would mean that suddenly we don’t have to pay people to do something with it – they’ll be fighting to collect it. Main issue is if someone collects some “junk” that is actually a working satellite…..but that’s a problem for another day.